The present invention is directed to one part moisture curable sealants based on silyl terminated polyethers (MS sealants).
One part, moisture cure sealants based on silyl-terminated polyethers (MS sealants) are a preferred construction sealant in certain areas of the world. In Japan, for instance, MS sealants have become a preferred type of construction sealant since their introduction over 20 years ago.
MS sealants have versatile and well-balanced properties. Some of the attractive properties of MS sealants include, but are not limited to, 100% solids content, low temperature gunnability, storage stability, weather resistance, stain resistance, and adhesion to various substrates. The combination of the performance of 100% silicone with the paintability of an organic are particularly attractive features.
MS polymer contains siloxane bonds upon curing, yet the main chain portion is a polyether which provides excellent paintability with water based acrylic paints. With xe2x80x9coil basedxe2x80x9d alkyd type paints, however, MS sealants exhibit very long dry times, i.e in excess of 4 days, and others do not dry at all when applied to current MS sealants.
It would be desirable to develop MS sealant compositions that when painted with oil based alkyd paints, provide substantially reduced dry times of the oil based paints, i.e. do not interfere with the normal drying/curing process of the alkyd paints.
In one aspect, the present invention is directed to an MS sealant composition with improved paintability with alkyd paints, comprising:
a) a moisture curable polymer of the formula (I): 
where a+b=3 and a is 1, 2 or 3, Q is a monovalent hydrocarbon radical having from one to forty carbon atoms where each X is independently a hydrolyzable group selected from the group consisting of methoxy, acetoxy, and oxime and m and n are non-zero integers chosen so that the weight average molecular weight ranges from about 5,000 to about 45,000;
b) a condensation catalyst;
c) a silane crosslinking agent; and
d) a hydrocarbon processing aid.
The present invention relates to a curable resin composition comprising an oxyalkylene base copolymer having at least one silicone atom containing group to the silicone atom of which a hydroxyl group and/or hydrolyzable group is attached and which is cross-linked through formation of a siloxane bond. More particularly, the present invention relates to the above curable silyl-terminated oxyalkylene base compositions with improved paintability performance with oil base alkyd paints. The oil based alkyd paints may have, for instance, paint dry times greater than or equal to 24 hours under ambient laboratory conditions.
The cause of the elongated drying times of the oil base paints with MS sealants is leaching of the organic plasticizing fluids form the crosslinked MS elastomeric sealant into the alkyd paint topcoating thereby interfering with the drying mechanism of the alkyd paints. Commonly used organic plasticizing fluids found in current MS sealants that will leach into alkyd paint topcoats include polyalkylene glycols (such as UCON LB285), the family of phthalate esters including butylbenzy phthalate, dioctylphthalate, and the family of benzoates including dipropyleneglycol dibenzoate, diethyleneglycol dibenzoate, propyeleneglycol dibenzoate, dimethanol dibenzoate, isodecyl benzoate, neopentyl glycol dibenzoate, and pentaerythritol tetrabenzoate.
MS sealant alkyd paint performance can be improved by simply removing the above plasticizing fluids. However, since the above organic fluids function as diluents, removal of the organic plasticizers gives MS sealants with a greatly reduced extrudability, a significant disadvantage in the construction market. In the present invention, it was unexpectedly found that the use of a hydrocarbon fluid containing greater than 40 parts by weight of cyclic paraffinic hydrocarbons and less than 60 parts by weight of noncyclic paraffinic hydrocarbons as a plasticizing fluid in MS sealants vastly improves the drying time of the alkyd paints while maintaining the extrusion rate. CONOSOL 200 is one example of such a hydrocarbon fluid.
The present invention relates to an MS sealant composition with improved paintability with alkyd paints comprising:
a) a moisture curable polymer of the formula (I): 
where a+b=3 and a is 1, 2 or 3, Q is a monovalent hydrocarbon radical having from one to forty carbon atoms where each X is independently a hydrolyzable group selected from the group consisting of methoxy, acetoxy, and oxime and m and n are non-zero integers chosen so that the weight average molecular weight ranges from about 5,000 to about 45,000 where each X is independently a hydrolyzable group selected from the group consisting of methoxy, acetoxy, and oxime and m and n are non-zero integers chosen so that the weight average molecular weight ranges from about 5,000 to about 45,000, preferably from about 6,500 to about 40,000, more preferably from 8,000 to about 35,000 to about and most preferably from about 10,000 to about 30,000;
b) a condensation catalyst;
c) a silane crosslinking agent; and
a) a liquid paraffinic hydrocarbon processing aid preferably comprising, based on 100 parts by weight of the hydrocarbon fluid, greater than 40 parts by weight (greater than 40 wt. %) of cyclic paraffinic hydrocarbons and less than 60 parts by weight (less than 60 wt. %) of noncyclic paraffinic hydrocarbons.
The condensation catalyst used to effect cure of the composition may be any of several known in the art, especially those based on tetravalent titanium or tetravalent tin. It should be noted that the dialkyl tin dicarboxylate catalysts frequently used as condensation cure catalysts do not work well in these formulations and should be generally avoided. Preferred catalysts are selected from the group consisting of di-alkyl tin bis acetylacetonate compounds with butyl especially preferred, di-alkyl tin phthalate ester (with butyl especially preferred available from Witco Chemical Company) and di-isopropoxytitanium bis-acetylacetonate.
The composition may contain optional additives, including inorganic fillers, such as stearic acid treated calcium carbonate, silane adhesion promoter, thermal/UV stabilizers, thixotropes, and pigments. One example of suitable MS curable polymers can be found in U.S. Pat. No. 3,971,751, incorporated herein by reference in its entirety; in particular the polyether having a silylether at each end of the molecule, and disclosed in columns 4 and 5 of the aforementioned patent.
In a preferred embodiment, the MS sealant of the present invention comprises, based on 100 parts by weight (pbw) of the sealant composition, from 15 to 90 pbw, more preferably from 20 to 60 pbw, more preferably from 30 to 50 pbw of the moisture curable MS polymer of formula I; from 0.1 pbw to 10 pbw, more preferably from 0.2 pbw to 5 pbw, more preferably form 0.5 pbw to 1 pbw of a condensation cure catalyst; from 0 to 80 pbw, more preferably from 10 to 70 pbw, more preferably from 30 to 60 pbw of calcium carbonate filler; from 0.1 to 10 pbw, more preferably from 0.4 pbw to 5 pbw, and more preferably from 0.7 pbw to pbw of a methoxysilane crosslinking agent such as methyl or vinyl trimethoxysilane); from 0 to 5 pbw, more preferably from 0.3 to about 2 pbw, more preferably from 0.5 to 1.5 of an organosilane adhesion promoter(such as aminoethyl-aminopropoyltrimethoxy silane); from 0 to 10 pbw, more preferably from 0.5 to about 7 pbw, and most preferably from 1.5 to 5 pbw of a thixotropic agent (such as fumed silica or nonreactive polyamide); from 0 to 1 pbw, more preferably from 0.1 to 0.8 pbw, and most preferably form 0.2 to 0.5 pbw of a hindered amine stabilizer, such as TINUVIN 770 (available from Ciba-Geigy) from 0 to 1 pbw, more preferably from 0.1 to 0.8 pbw, and most preferably from 0.2 to 0.5 pbw of a UV absorber such as TINUVIN 327; from 0 to 10 pbw, more preferably from 1 to 7 pbw, and most preferably from 2 to 5 pbw of a pigment, such as TiO2; and from 1 to 20 pbw, more preferably form 2 to 10 pbw, and more preferably from 4 to 8 pbw of a hydrocarbon processing aid.
In a preferred embodiment, the hydrocarbon fluid comprises one or more cyclic hydrocarbons containing 5 to 24 carbon atoms per molecule, and optionally, one or more non cyclic paraffinic hydrocarbons containing from 5 to 24 carbons per molecule. In a preferred embodiment, the cyclic and non cyclic hydrocarbons of the hydrocarbon fluid each contain from 8 to 20, more preferably from 10 to 15 carbon atoms per molecule. Suitable cyclic paraffinic hydrocarbons include, for example cyclohexane, cyclooctane, cyclononane, cyclododecane. Suitable noncyclic paraffinic hydrocarbons include, for example n-heptane, n-octane, iso-octane, n-nonane, n-decane, n-undecane, n-dodecane, iso-dodecane, n-heptadedecane, n-octadecane, n-eicosane, isoeicosane. In a preferred embodiment, the hydrocarbon fluid comprises less than about 0.5% by weight aromatic hydrocarbons.
The following examples are to illustrate the invention and are not to be construed as limiting the appended claims.